This invention relates to a cleaning apparatus for cleaning a substrate, such as a semiconductor substrate or wafer and a liquid crystal plate, which are required to have a high degree of cleanliness.
With recent rapid progress in technology for fabricating high-integration semiconductor devices, circuit-wiring patterns have been becoming increasingly fine and, as a result, spaces between wiring patterns have also been decreasing. Especially, in photolithography for formation of wiring patterns with a spacing of less than 0.5 microns, as depth of focus becomes shallower, it is required for an image-formation surface to have an exceptionally high degree of flatness. In addition, it is required for semiconductor substrates to be subjected to fine cleaning in such a manner as to remove sub-micron particles from surfaces on which wiring patterns are to be formed, which particles might otherwise cause short circuits between adjacent wiring patterns. Such fine cleaning is also required in processing a glass substrate to be used as a masking member, a liquid crystal plate or the like.
FIG. 4 illustrates a conventional semiconductor substrate polishing apparatus for conducting fine cleaning as well as planarization or polishing of semiconductors. The apparatus comprises a polishing section 10, a loading/unloading section 22, a transfer section including two transfer machines 24a, 24b, a cleaning section including three cleaning machines 26a, 26b, 26c, and a turning-over machine 28. Semiconductor substrates to be polished are loaded into the loading/unlading section 22 and, then, transferred to the polishing section 10 by transfer machines 24a, 24b. Following completion of polishing in the polishing section 10, the substrate is returned to the loading/unloading section 22 through the cleaning section where the substrate is cleaned by the cleaning machines 26a, 26b, 26c and finally dried.
The transfer machines 24a, 24b may be of a mobile type or of a stationary robot type having articulated arms provided with robot hands. As shown in FIG. 5, the polishing section comprises a turntable 12 provided on its upper surface with a polishing cloth 11, a substrate carrier 13 for holding a substrate W and bringing it into contact with the polishing cloth 11 to subject the substrate W to polishing, and a nozzle 14 for supplying an abrasive slurry Q (for example, when polishing a dielectric layer or oxide film formed over a silicon substrate, a slurry comprising an alkali solution containing abrasive particles of a predetermined size) to the polishing cloth 11 during polishing of the substrate W.
With reference to FIGS. 6(a)-6(c), the first cleaning machine 26a comprises a plurality of upright substrate support rollers 30 which have annular grooves at their upper ends adapted to be engaged with a peripheral edge of a substrate W to hold the substrate in a horizontal state, and which rotate about their own vertical axes to rotate the substrate at a low speed. The first cleaning machine 26a further includes a pair of scrub cleaning rollers 40a, 40b made of a sponge material or the like which are adapted to be engaged with upper and lower surfaces of the substrate W while it is held and rotated by the rollers 30, respectively, to effect scrub polishing of these surfaces. Each of the scrub cleaning rollers 40a, 40b is movable in a vertical direction between a polishing position for effecting the above-stated scrub cleaning, and a retracted position.
With reference to FIG. 8, the second and third cleaning machines 26b and 26c each comprise a disc 36 provided on a top end of a rotational shaft 32, which disc is provided with a plurality of substrate holding arms 34 extending radially outwardly from a peripheral edge of the disc. The holding arms 34 are provided with upright chuck portions 34xe2x80x2 at their tip ends for chucking a substrate W. Further, the cleaning machines 26b, 26c comprise a scrub cleaning member 38 made of a sponge material or the like which is provided on a distal end of an arm 37 which is supported at its proximal end on a top end of a pivotal shaft 35, and nozzles 39, 40 for supplying cleaning liquid and pure water, respectively, to the substrate W during polishing thereof.
Upon completion of polishing of a substrate W in the polishing section 10, the cleaning machines 26a, 26b, 26c effect cleaning of the substrate W as follows.
The substrate W is firstly transferred to the first cleaning machine 26a, in which the rollers 30 hold and rotate the substrate about its axis and, simultaneously, the scrub cleaning rollers 40a, 40b engage with the upper and lower surfaces of the substrate, respectively, to remove particles such as abrasive particles and/or substrate debris from these surfaces, while pure water and/or cleaning liquid is supplied to the surfaces.
Following scrub cleaning by the first cleaning machine 26a, the substrate W is transferred successively to the second and third cleaning machines 26b and 26c, where it is held and rotated by chucks 34xe2x80x2 at around 100-500 rpm while the scrub cleaning member 38 engages with and sweeps the upper surface of the substrate W, while being rotated about its vertical axis, to thereby effect scrub cleaning of the upper surface. During polishing, the nozzles 39, 40 supply pure water and/or cleaning water, to which mega-sonic vibration may be imparted. Upon completion of the scrub cleaning in the third cleaning machine 26c, speed of rotation of the substrate W is increased to 1500-5000 rpm to effect spin drying of the substrate, while a clean inert gas is supplied around the substrate as required. The dried substrate is thereafter returned to the loading/unloading section 22 by the transfer machine 24b. 
As shown in FIG. 4, the polishing apparatus is enclosed in a housing to prevent particles such as abrasive particles and substrate debris from scattering outside the apparatus and, further, the respective sections in the housing including the polishing section 10 and the cleaning section are divided by partition walls which function to prevent particles from being carried to sections other than the polishing section 10. Further, each of the separated sections is preferably provided with an air-conditioning system for generating an air flow flowing around a substrate treated therein in a downward direction to prevent particles including abrasive particles and substrate debris from scattering outside the section.
The apparatus involves a problem in connection with the first cleaning apparatus 26a as follows.
In order to effect scrub cleaning of the entire upper and lower surfaces of a substrate W, the scrub cleaning rollers are brought into contact with the surfaces along a diameter of the substrate in such a manner that, as shown in FIG. 7(a), the scrub cleaning rollers extend, and opposite ends thereof are positioned outside a peripheral edge of the substrate to enable the rollers to engage with the entire opposite side surfaces of the substrate during cleaning. However, as shown in FIG. 7(b), a clearance gap S exists between the upper and lower scrub cleaning rollers 40a and 40b around peripheral edge B of the substrate W and, as a result, the peripheral edge, specifically a bevel portion thereof is unable to be scrub cleaned. If particles such as abrasive particles remain on the peripheral edge due to incomplete cleaning, there is a possibility that these particles will be displaced or distributed to the side surfaces of the substrate and produce defects in the substrate such as short circuits between adjacent wiring patterns.
To solve this problem, there has been proposed a cleaning device designed specifically for cleaning the peripheral edge of a substrate and adapted to be incorporated into a conventional cleaning machine. However, inclusion of such a device causes the polishing apparatus to become complicated in construction and control and expensive in installation and maintenance.
An object of the present invention is to provide a substrate cleaning apparatus provided with an edge-cleaning device which is simple in construction and easy to control.
In accordance with the present invention, there is provided a substrate cleaning apparatus comprising a side surface cleaning member and a peripheral edge cleaning member. The side surface cleaning member includes a cylindrical scrub cleaning body having a cylindrical surface and opposite ends. The cylindrical scrub cleaning body is adapted to be rotated about its axis with the cylindrical surface thereof engaged with a side surface of a substrate to be cleaned to effect scrub cleaning of the side surface. The peripheral edge cleaning member is adapted to be engaged with a peripheral edge of the substrate to effect scrub cleaning of the peripheral edge.
The peripheral edge cleaning member may be attached to one of the opposite ends, of the cylindrical scrub cleaning body so as to be rotated along with the cylindrical scrub cleaning body about the axis of the cylindrical scrub cleaning body. The peripheral edge cleaning member may comprise a sponge member adapted to be engaged with and scrub the peripheral edge of the substrate. The sponge member may be made of a PVA, a urethane foam or the like. The cylindrical scrub cleaning body may also be made of the same material as the sponge member as stated above and integrally formed with the sponge member.
The side surface cleaning member is adapted to be placed on the side surface of the substrate to be cleaned in such a manner that the axis of the cylindrical cleaning body is parallel to the side surface of the substrate while the end provided with the peripheral edge cleaning member is positioned inside the peripheral edge of the substrate, with the peripheral edge cleaning member positioned outside the peripheral edge and the sponge member thereof engaged with the peripheral edge. The other end of the cylindrical scrub cleaning body is positioned outside the peripheral edge, whereby the entire side surface and the entire peripheral edge of the substrate are able to be to scrub cleaned.
The peripheral edge cleaning member may comprises a plurality of bristles instead of the cylindrical sponge member. The bristles may be made of mohair, fluorine-containing resin or the like.
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings.